Add role switcher (Client/Seller) in navigation menu

- Add role switcher buttons after Explore/Quote/Кабинет with separator
- Dynamic center tabs based on role: BUYER shows orders/addresses, SELLER shows offers
- Redirect to appropriate page when switching role in client area
- Add localization for roles.client and roles.seller

i18n/locales/en/cabinetNav.json

@@ -14,6 +14,10 @@
     "seller": "Seller",
     "suppliers": "Suppliers",
     "hubs": "Hubs",
-    "ai": "AI assistant"
+    "ai": "AI assistant",
+    "roles": {
+      "client": "I'm a client",
+      "seller": "I'm a seller"
+    }
   }
 }

i18n/locales/ru/cabinetNav.json

@@ -14,6 +14,10 @@
     "seller": "Продавец",
     "suppliers": "Поставщики",
     "hubs": "Хабы",
-    "ai": "AI ассистент"
+    "ai": "AI ассистент",
+    "roles": {
+      "client": "Я клиент",
+      "seller": "Я продавец"
+    }
   }
 }